Tubular metal sidewalls for containers possessing balanced strength and containers made therewith



Oct. 14, 1969 F. E. ULLMAN TUBULAR METAL SIDEWALLS FOR CONTAINERS POSSESSING BALANCED STRENGTH AND CONTAINERS MADE THEREWITH 4 Sheets-Sheet 1 Filed NOV. 30. 1967 MMM lffdklv'nr.

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TUBULAR METAL SIDEWALLS FOR CONTAINERS POSSESSING BALANCED STRENGTH AND CONTAINERS MADE THEREWITH Filed Nov. 50. 19a? 4 Sheets-Sheet Oct. 14, 1969 F. E. ULLMAN 3.472,418

TUBULAR METAL SIDEWALLS FOR CONTAINERS POSSESSING BALANCED STRENGTH AND CONTAINERS MADE THEREWITH Filed Nov. 30, 1967 4 Sheets-Sheet 3- w/w/m v4 tri Q I I zawwzk 1/ ii 1/ 3/ .1/ i/ 1/ zZiiz? Oct. 14, 1969 E, N- 3,472,418

TUBULAR METAL SIDEWALLS FOR CONTAINERS POSSESSING BALANCED STRENGTH AND CONTAINERS MADE THEREWITH Filed Nov. 30. 1967 4 Sheets-Sheet 1.

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United States Patent 3,472,418 TUBULAR METAL SIDEWALLS FOR CONTAINERS POSSESSING BALANCED STRENGTH AND CON- TAINERS MADE THEREWITH Frederick E. Ulirnan, Winnetka, Ill, assignor to Inland Steel Company, Chicago, Ill., a corporation of Delaware Filed Nov. 30, 1867, Ser. No. 686,893 Claims priority, application Great Britain, Feb. 27, 1967, 9,200/67 Int. Cl. B65d 7/46 U.S. Cl. 220-72 10 Claims ABSTRACT OF THE DISCLOSURE A shaped metal sidewall for shipping containers formed of relatively thin lightweight sheet metal, and improved containers formed thereby, wherein provision is made for strengthening those regions of the container sidewall viz, the end portion or portionswhich are particularly subject to damage and/or failure as a result of heavy axial or oblique loading, yet wherein this is accomplished by the particular shape imparted to the container and without the need for any additional reinforcing members other than those conventionally employed.

Cross reference to related applications Hans R. Luedi, Ser. No. 431,388, filed Feb. 9, 1965, now U.S. Patent No. 3,357,229.

Background of the invention The present invention relates to shipping containers and, more particularly, to improved relatively thin, lightweight metallic container sidewalls, and to improved containers made therewith, which containers are of the type commonly used in transporting or storing oil products, and other liquid, semiliquid, pulverized, or granular substances. In its principal aspects, the invention is concerned with improved container sidewall constructions, wherein those regions of the container sidewall most susceptible to damage and/ or failure (such as the ends or the extremities thereof) are shaped so as to optimize the strength characteristics of the container and, particularly, the resistance of the container to damage resulting from excessive axially or obliquely applied loads such as often occur when a filled or partially filled container is dropped on its end.

For a number of years there has been a persistent and increasing demand for a sturdy, light-weight shipping container which is not only capable of withstanding the rigors of transportation from the supplier to the consumer, but which is also more resistant to deformation forces during periods of storage and use. In an effort to meet the foregoing demand, there has been a recent trend by manufacturers towards the use of thinner and lighter sheet metal in the construction of both the sidewalls and the drum heads, thus minimizing the amount and weight of materials used and, therefore, both the manufacturing and transportation costs.

Let it be assumed that a SS-gallon drum is required by a consumer for use in a specified application, or range of applications. Such a drum, in order to meet the requirements of the consumer, must have or exceed minimum acceptable standards of strength which, merely by way of example, heretofore required the use of 18-gauge sheet steel. However, manufacturers have, consistent with the recent trend, attempted to make such drums of ZZ-gauge, or even 24-gauge, sheet steel rather than the heavier 18- gauge material, while at the same time providing drums which meet or exceed the consumers minimum acceptable standards of strength and which are, therefore, strong enough to be suitable for use in the same applications as drums made of the heavier gauge material.

As used herein, the term strong enough is intended to connote a drum characterized by its ability to withstand the rigors of transportation under unfavorable conditions during one trip without developing a leak. The drum may be deformed, but the construction should be such that those deformations that are caused by the kinds of mistreatment of filled drums usually encountered during transportation do not promote the creation of sharp wrinkles or folds, since these often rapidly develop into leaks.

The recent trend towards the use of thinner and lighter sheet material in the construction of drums has, however, simply magnified the problems of deformation, rupture, and attendant leakage or spoilage of the contents of such drums, since such thin gauge material has presented particularly difficult problems with respect to its ability to withstand deformation forces of the type commonly encountered during handling, transportation and storage.

Indeed, it has been found to be very difiicult to find a satisfactory compromise between the various requirements that drums must meet to conform to acceptable standards-requiren1ents that are generally conflicting in nature in that the drums must not only be characterized by their strength, but also must be made of material which, in itself, is not as strong as that heretofore used. For example, it would serve no useful purpose to provide a light-weight drum which has a great resistance to axial forces but which collapses under a small radial load. Conversely, a drum which is highly resistant to radial loads but which collapses under small axial forces is not satis factory. Moreover, a satisfactory drum must also possess characteristics of resistance to forces caused by oblique drops where the drum hits the ground with part of its chime. Even a drum which has sufiicient strength, and what might be termed balanced strength in all the foregoing respects would not be satisfactory if it could not stand being rolled over a reasonable distance.

With the above considerations in mind, the container industry has devised and adopted a great number of tests of different nature for the purpose of evaluating various drum constructions with regard to both the foregoing and other requirements. Such tests are primarily intended to simulate those various types of unfavorable conditions normally encountered during handling, transportation, and storage of drums in the field.

Notwithstanding the difiicult problems, conflicting structural requisites, and conflicting design considerations heretofore encountered, generally satisfactory and commercially accepted sheet metal containers which can be made of 24-gauge metal have heretofore been developed. Exemplary of such containers and their methods of manufacture are those containers disclosed in M. J. M. Coppens U.S. Patent Nos. 3,268,108 and 3,268,109, issued on Aug. 23, 1966, and assigned to the assignee of the present invention. Such known containers are generally characterized by the provision of a generally cylindrical sidewall having a pair of end members rigidly seamed to respective ones of the opposite sidewall extremities; the sidewall being provided with a plurality of radially outwardly extending equidiameter peripheral beads spaced axially from one another with the spacing between beads defining a plurality of radially inwardly extending equidiarneter peripheral furrows, and wherein the top portion of each of the beads and the bottom portions of the adjacent furrows define a smoothly curved radial cross-section; and with the connections between the sidewall and the end members being offset radially inwardly of the beads and furrows.

Although such known containers have proven satisfactory for most conditions of use, have given excellent results under varying conditions of severe treatment, and have been found commercially acceptable, it has been found that certain areas of the containers are somewhat more prone than desirable to damage and/or fracture resulting in leaks when subjected to severe treatment resulting in excessive axially r obliquely applied load conditions. For example, when a filled or partially filled container of the foregoing type was dropped axially or in an inclined position, and then subsequently subjected to vibrations, it was found that the region including the head or beads at or near the end of the sidewall and/ or the transition of the last bead to the chime was, on occasion, badly deformed by the excessive axially and/or obliquely applied load conditions. Such deformation subsequently developed into a leak when the container was later subjected to vibrations.

Accordingly, it is a general aim of the present invention to overcome the foregoing disadvantages by providing improved shaping container sidewallsparticularly those made of relatively thin light-weight sheet metalwhich serve to optimize the strength characteristics of the resultant product, and wherein this is accomplished without having to provide separate reinforcing members other than those conventionally employed.

It is another object of the invention to provide improved containers and sidewalls which permit use of commercially available container forming apparatus and processes with only minor alterations thereto, yet which can produce containers having all of the desirable characteristics disclosed in the aforesaid patents of M. J. M. Coppens, while at the same time being considerably more resistant to excessive axially and/or obliquely applied load conditions.

Other objects and advantages of the invention will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevation of an exemplary conventional shipping container of the type illustrated in the aforesaid M. J. M. Coppens patents;

FIG. 2 is an enlarged, fragmentary longitudinal section of a portion of the sidewall of the conventional container shown in FIG. 1, and illustrating also details of the exemplary chime construction used for connecting an end member, or drum head, to the sidewall;

FIG. 3 is a fragmentary sectional view similar to FIG. 2, but here depicting a container sidewall made in accordance with the present invention and illustrating particularly the progressive reduction in bead diameter adjacent at least the lower extremity of the sidewall;

FIG. 4 is a fragmentary side elevational view of a shipping container made in accordance with one form of the present invention, here showing the progressive reduction of bead diameters adjacent the lower extremity of the sidewall;

FIG. 5 is a fragmentary side elevational view of a slightly modified container sidewall wherein the beads adjacent both the upper and the lower extremities are of progressively reduced diameters;

FIG. 6 is a vertical half-section of one exemplary conventional type of head forming apparatus which has here been modified to permit formation of a container sidewall similar to that shown in FIGS. 3 and 4 (the modifications having been exaggerated in scale for purposes of clarity), the apparatus here being illustrated prior to initiation of a heading operation;

FIG. 7 is a view similar to FIG. 6, but here showing the apparatus with the endmost die segments fully expanded and with the remaining die segments partially expanded during an intermediate point in the expanding operation;

FIG. 8 is a view similar to FIG. 6, but here depicting a different type of conventional expanding apparatus which has also been modified to permit formation of a container sidewall similar to that shown in FIGS. 3 and 4,

the modifications again having been shown in exaggerated form for purposes of clarity; and,

FIG. 9 is a view similar to FIG. 7, but here depicting still another type of conventional expanding apparatus which has here been modified (as shown in an exaggerated manner for clarity) to permit formation of a container sidewall similar to that shown in FIG. 5.

While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention.

Conventional container sidewall constructions Referring now to the drawings, there is illustrated in FIG. 1, an exemplary shipping container or drum 1t) having a generally cylindrical body or sidewall 11 formed from a cylindrical or tubular blank or body portion 12. The drum 10 is here of the type disclosed in the aforesaid M. J. M. Coppens patents. The opposite ends of the drum are closed by a pair of disc-shaped end members 13 which are respectively secured to the opposite extremities of the sidewall 11 by a curled seam or chime 14.

In order to enhance the characteristics of drum strength and resistance to deformation forces, provision is made in the illustrative conventional drum construction for concentrating the metal in the vicinity of the chime 14, thus substantially reinforcing the drum and permitting the latter to be tipped on its edge and rolled on the chime so as to facilitate movement thereof. To this end, and as best illustrated by reference to FIG. 2;, the chime 14 is defined by adjacent layers or plies of the sidewall 11, the drum head or end 13, and an annular metallic reinforcing ring 15. As here shown, the exemplary chime is comprised of eight pliesthere being two plies 11a, 11b of sidewall material 11, three plies 13a, 13b, of end material 13, and three plies 15a, 15b, of reinforcing ring material 15.

In formation of the eight-ply chime 14', for example, by bending, turning, rolling or similar manufacturing procedures well known to those skilled in the art, the outer-most extremities of the reinforcing ring 15 and end 13 are bent or turned over into a substantially U-shaped configuration encompassing the extremity of the sidewall 11. The entire connection, including the extremity of the sidewall 11, is then bent or turned over again into a second substantially U-shaped configuration. Thus, the marginal edge of the sidewall is bent once through an angle of into a U-shape whereas the marginal edges of the ring 15 and end 13 are bent twice through angles of 180 into a double U-shape. In the exemplary chime, therefore, the inner ply 15a of the ring 15 abuts the inner ply 13a of the end, while the outer ply 15b of the ring abuts the outer ply 13b of the end. The intermediate ply 150 of the ring is received between the inner ply 11a of the sidewall 11 and the intermediate ply 13c of the end, while the outer ply 11b of the sidewall is accommodated between the intermediate and outer plies of the end 13. Thus, the plies 11a, 13a, 15a, 11b, 13b and 15b define an inverted U-shaped configuration, While the plies 13b, 15b, 13c and 15c define a U-shaped configuration.

The provision of an eight-ply chime with containers constructed in accordance with the invention has various advantages. For example, the connections between the sidewall 11 and the ends 13 are reinforced, thus minimizing the danger of deformation of the chime and separation of the end and sidewall. At the same time, the radial thickness of the chime is increased, particularly where the wall thickness of the ring 15 is greater than that of the sidewall 11, as shown in the exemplary construction of FIG. 2. Such an increase in overall thickness of the chime materially reduces the risk of a chime cutting into the sidewall of an adjacent drum where the drums are shipped so that their longitudinal axes are other than parallel, for example, where their axes are perpendicular to one another.

The drum (FIG. 1) may, in a conventional manner, be provided with a suitable filling and discharge opening and a vent hole. Such openings may conveniently be formed in one end member 13 and closed by means of separable bungs, plugs, screw caps, or similar closure devices, here shown generally at 16 and 18. Moreover, as disclosed in the aforesaid M. J. M. Coppens patents, the drum body or sidewall 11 is formed over substantially its entire length with a plurality of radially outwardly extending equidiameter peripheral beads having a diameter D" separated by a plurality of radially inwardly extending equidiameter peripheral furrows, with the alternate beads and furrows being so interrelated and associated with one another as to form a container sidewall construction which exhibits excellent performance characteristics in terms of balanced strength and resistance to most deformation forces. In the exemplary sidewall construction shown in FIG. 1, twenty-six such beads 19 are formed in the sidewall 11, the beads being respectively spaced apart by twenty-five furrows 20.

Of course, while twenty-six beads 19 and twenty-five furrows 20 have been shown, it will be understood that the particular number of beads and furrows may vary without departing from the invention. By way of example, a 55-gallon drum will generally include from twentythree to twenty-seven beads alternating with twenty-two to twenty-six furrows, assuming, of course, that the drum is of generally standard overall dimensions, i.e., 0n the order of approximately thirty-two inches in height (as measured from end member to end member) and formed from a cylindrical blank having an inside diameter D of approximately twenty-two and one-half inches.

As best illustrated by reference to FIG. 2, the top portion of each of the beads 19 and the bottom portion of each of the furrows 20 have a smoothly curved radial cross-section, and respective ones of the flanks of each head blend smoothly into a flank of each of the adjacent furrows. In the exemplary construction shown in FIG. 2, the radial cross-section of each bead 19 and of each furrow 20 comprise circular arcs which blend directly into one another.

Containers and sidewalls made in accordance .with the present invention As thus far described, the container 10 shown in FIGS. 1 and 2 is well known and described and claimed in the aforesaid M. I. M. Coppens patents. However, while such containers have been found to possess excellent performance characteristics when subjected to normal types of usage and treatment, they have also been found, as indicated above, to be susceptible to damage and/or fracture at particular regions of the container when subjected to certain types of severe treatment or mistreatment such, for example, as excessive axially or obliquely applied load conditions resulting in deformation of the container in such regions, followed by periods of vibration which tend to produce leaks in the deformed area of the container. Referring to FIGS. 1 and 2, those regions of the container which have been found subject to the foregoing drawback have been generally indicated at 21. Two such regions 21 are present in any given containercne near each extremity of the container, with each region including the unexpanded portion of the blank 12 and at least the endmost bead 19 and furrow 20, The particular number of beads 19 and furrows 20 included within the re gion 21 may differ dependent upon numerous variables such as the dimensions of the container, the material from which it is made, and the thickness of such material. However, when dealing with steel shipping drums of the type shown in FIGS. 1 and 2, made of 24-gauge sheet steel and having on the order of twenty-six beads, it has been found that each region 21 will generally include on the order of three beads 19 and three furrows 20.

In accordance with one of the important aspects of the present invention, provision is made for improving the balanced strength characteristics of beaded metal containers in the regions 21 adjacent the extremities of the container 10 by enhancing the resistance of the material in such regions to excessive axially and/or obliquely applied loads. To accomplish this, advantage is taken of the fact that the beads 19 and furrows 20 have heretofore been provided for the purpose of increasing the resistance of the sidewall 11 to radial loads, while at the same time retaining as much resistance as possible to axial loads. However, such beads 19 and furrows 20 do serve to reduce the resistance of the sidewall 11 to axially or obliquely applied loads. Thus, when provided with deeper beads 19 and furrows 20, the sidewall 11 will be stronger radially, but weaker axially. Conversely, with shallower beads and furrows, the sidewall will be weaker radially and stronger axially. To obtain the objectives of the present invention, the sidewall is formed during a heading operation with n axially spaced beads and furrows (where n is any desired whole integer) which are progressively greater in diameter as their axial distance from the end member 13 or chime 14 increases, yet wherein the beads are, in all instances, smaller in diameter than the diameter D" of the beads 19 in the central portion of the container sidewall 11.

In keeping with the present invention, and as best illustrated in FIGS. 3 and 4, a container 10 is formed with a first plurality of equidiameter beads 19 having diameters D" (D" being greater than the diameter D of the blank 12 from which the tubular sidewall 11 is formed) and a plurality of alternating equidiameter furrows 20, the beads 19 and furrows 20 in this exemplary form of the invention comprising the uppermost twenty-three beads and the intervening twenty-two furrows. The three beads and furrows adjacent the lower extremity of the container 10-i.e., those within the region 21are formed with progressively increasing diameters as measured from the end member 13 or chime 14 to the lowermost bead 19 outside the region 21, as best indicated at 19a, 19b, 19c and 20a, 20b, 200. Thus, the lowermost bead 19a has a diameter D which is greater than the diameter D of the blank 12 but less than the diameter D" of the beads 19. Similarly, the heads 1% and 19c are each progressively larger than the bead 19a, but progressively smaller than the beads 19. The arrangement is such that the beads 19a, 19b, 19c and the furrows 20a, 20b, 200 are shallower than the beads 19 and furrows 20 respectively, thus increasing the resistance of the sidewall material in the region 21 to axial and/or oblique loads. It has been found that such increase in resistance to axial and/or oblique loads materially improves the balanced strength characteristics of the container 10', while the slight decrease in resistance to radial loads in the region 21 does not materially alter the performance characteristics of the container.

Thus far, the invention has been described in conjunction with a method of forming a container 10' in which the beads and furrows at only one end of the sidewalk-viz, the lower end as viewed in FIGS. 3 and 4- progressively differ in diameter so as to form a tapered drum extremity having the desired characteristics in terms of balanced strength. This is, of course, consistent in scope with the invention since it is normally the lower end of the container, particularly a filled or partially filled container, which is most susceptible to damage when the container is dropped or is in transit. However, those skilled in the art will appreciate that it may, in some instances, be desirable to form only the top of the container, or, more likely, both ends of the container, in accordance with the invention. An example of the latter construction has been illustrated in FIG. 5, wherein it will be observed 7 that the uppermost three beads 19d, 19e, 19 and furrows d, 20e, 29 in a region designated at 21 (respectively corresponding to the beads 19a, 19b, 19c and furrows 20a, 20b, 200 in region 21) also progressively increase in diameter so as to form a container 10 in which both extremities are tapered.

Referring to the known prior art constructions illustrated in FIGS. 1 and 2, and to the aforesaid M. J. M. Coppens patents, it will be observed that one of the advantages resulting from such a construction is that the chime 14 and its immediately proximate area is offset radially inwardly from the beads 19 and furrows 20. This is particularly desirable since the chime area of the container 10 is particularly vulnerable when, for example, the container is rolled on its side. Consistent with this desirable characteristic, provision is made when forming the sidewalls for the containers 10 (FIGS. 3 and 4) and 10" (FIG. 5), to achieve the same result. Thus, it will be best observed upon reference to FIG. 3 that the outside diameter of chime 14 is not only smaller than the diameters D of the beads 19 and the cylindrical surface (designated at 22) defined by tangent lines drawn through the beads 19, but, it is also smaller than the diameters of all the beads 19a, 19b and 190. Moreover, the latter beads are, in the exemplary arrangement, dimensioned so that lines drawn tangent thereto lie in a frusto-conical surface (designated at 24) which also passes the chime 14 in outwardly spaced relation thereto. That is, the outside diameter of the chime 14 is smaller than the diameter of any circle (not shown) defined by the intersection of the frusto-conical surface 24 and any surface perpendicular to the vertical axis of the container and passing through the chime 14. To this end, the angle e defined by the intersection of the surfaces 22, 24 is preferably on the order of three to four degrees (3 4).

Apparatus for forming shaped metal sidewalls in accordance with the invention It will be appreciated by those skilled in the art that many forms of commercially available and/or known metal forming apparatus can be used to form containers in accordance with the present invention and, consequently, the particular apparatus selected does not constitute part of this invention. However, in order to facilitate an understanding of the invention, certain of the known types of exemplary metal forming apparatus have been illustrated diagrammatically in FIGS. 69 and will herein be described below, together with the alterations required to adapt such apparatus to carry out the process of the present invention.

Referring first to FIG. 6, there has been illustrated a portion of a typical bead forming apparatus of the type illustrated in the aforesaid copending application of Hans R. Luedi, Ser. No. 431,388, now US Patent No. 3,357,- 229 such apparatus being generally indicated at 25. As here shown, the apparatus 25 includes a frame 26, an actuator bar 28 and a drive plate 29. Mounted concentrically about the actuator bar 28 are a plurality of die units generally indicated at 30a-30e and 30n. The die units each comprise a plurality of die segments 31 which are held in annular relation by annular carrier plates 32, garter springs 34 and O-rings 35. The die segments 31 and carrier members 32 are provided with complementary inclined faces; the arrangement being such that as the actuator bar 28 and plate 29 are shifted to close towards the frame 26 (by any suitable power means, not shown), the adjacent carrier members 32 close axially upon one another and thus cam the die segments 31 and O-rings 35 outwardly to form beads in any cylindrical shell 12 mounted outboard of the die units. Various parameters can be adjusted to control the degree of radial outward movement of the die segments such, for example, as by adjusting the angle of inclination of the facing surfaces of the segments 31 and carrier members 32, or by adjusting the radial dimensions of the segments themselves.

In carrying out the present invention, the apparatus 25 has been modified in yet another wayi.e., by forming selected ones of the die segments 31 with integral shims which serve to limit the degree of relative closing movement between adjacent carrier members 32. To this end, selected ones of the die segments 31 in die unit 30a (which unit is to form the bead 19a in the sidewall 11 of FIGS. 3 and 4) are formed with an integral shim 36 having an axial thickness sufficient to permit only limited axial movement of the adjacent carrier 32 and, hence, only limited radial movement of the die segments 31 which are included in die unit 30a. Similarly, selected ones of the die segments 31 in die unit 30b (i.e., the unit which will form bead 1%) are provided with a shim 38. The axial thickness of the shim 38 is less than that of shim 36, thus permitting somewhat greater, but still only limited, expansion of the die segments. A still thinner shim 39 may be formed on selected ones of the die segments 31 in die unit 300 which will form the third bead 19c. As shown in FIG. 7, when the apparatus 25 is actuated, the carrier members 32 close to the left while the segments 31 move radially outward to form beads in the shell. As here viewed, the expanding operation has progressed to the point where the beads 19a, 19b, are fully formed, further expansion of these three beads being precluded by the shims 36, 38 and 39. The remaining beads 19 are here shown only partially formed, and as the plate 29 continues to move leftward they will be expanded to their full depth.

Referring next to FIG. 8, there has been illustrated a fragmentary portion of another typical known bead forming apparatus, generally indicated at 40, which is here similar to one of the types of apparatus disclosed in F. E. Ullman et al. US. Patent No. 3,349,599, assigned to the assignee of the present invention. In this construction a plurality of segmented die units 41a-41f and 4111 are slidably mounted on tapered expander bars 42, the latter being axially fixed but radially movable with respect to the frame 44 of the apparatus. A set of complementally tapered actuator bars 45 are drivingly coupled to a piston/ cylinder assembly 46 and slidably engaged with the tapered surfaces of the expander bars 42. The arrangement is such that as the actuator bars 45 shift to the left, the expander bars 42 move radially outward, thus expanding the segmented die units 41a41f and 4111 outwardly into expanding engagement with the blank 12 so as to form beads therein.

In this instance, the known expanding apparatus 40 has been modified to adapt it to carry out the process of the present invention by varying the radial lengths of the disc segments in selected ones of the die units. For example, to form a container of the type illustrated in FIGS. 3 and 4, the die units 41a, 41b and 416 are designed so as to expand localized peripheral areas of the blank 12 through progressively greater radial distances. To this end, the die unit 41a includes die segments 48 having a minimum radial height; die unit 41b includes die segments 49 which are somewhat longer in radial length than segments 48; and die unit 410 includes segments 50 which are longer than the segments 49 but shorter than the segments which are included in die units 41d-41f and 41m. Thus, when the expander bars 42 move radially outward during an expanding operation, the die units 41d 41 and 41n will engage the blank 12 prior to the units 41a, 41b and 41c. Thereafter the units 41c, 41b and 41a will engage the blank 12 in seriatim order. In other words, the working stroke of unit 41a will be relatively short, producing a relatively shallow bead 19a (FIG. 3); the working strokes of units 41b and 41c will be progressively longer, respectively producing progressively deeper beads 19b and 190 (FIG. 3); and the working stroke of die units 4141-41 and 41n will be equal and relatively long, thus producing relatively deep beads 19 .(FIG. 3).

The two types of expanding equipment shown in FIGS. 6 and 8 are somewhat similar in that they will each form a plurality of beads in a blank substantially at the same time. However, the method of the present invention can also be carried out in other types of known machines with suitable alterations. For example, there has been illustrated in FIG. 9 a portion of a bead forming apparatus, generally indicated at 51, which is of the type disclosed in L. A. N. Bijvoet US. Patent No. 3,349,600, assigned to the assignee of the present invention.

In this form of bead forming apparatus, a plurality of segmented die units 52 are carried by a cylindrical frame 54, each die unit including a plurality of segments 55 having guide pins 56 passing through the frame and terminating at their innermost radial ends in cam followers which here take form of rollers 58. As explained in greater detail in the aforesaid L. A. N. Bijvoet patent, the die segments 55 and their associated guide pins 56 may be staggered in adjacent guide units. Thus, as shown in FIG. 9, an axial section through the apparatus 51 will expose only guide pins 56 in every other die unit. An actuator bar 59, coupled to a suitable power cylinder 60 extends coaxially into the cylindrical frame 54, the bar 59 having a cam 61 on its leading end. The arrangement is such that when the bar 59 and its cam 61 are shifted axially through the die units 52, the cam 61 engages the cam followers 56 for the successive die units in seriatim order, thus expanding the die units outwardly and forming beads 19 in the blank 12 one at a time in sequential order.

In order to adapt apparatus of the type indicated at 51 in FIG. 9 for carrying out the process of the present invention to form, for example, a container such as shown in FIG. 5, the first three die units 52a, 52b, 52c and the last three die units 52d, 52e, 52f are designed so as to provide a relatively short working stroke for the units 52a, 52a, and progressively longer working strokes for die units 52b, 52c and for die units 52e, 52 the working strokes for all such units being shorter than those for the remaining die units 52. To accomplish this, the guide pins 56 associated with die units 52a-52c and with die units 52d-52f (only guide pins 56a, 56c and 56:; being visible in FIG. 9) are made progressively longer, with all being shorter than the guide pins 56 associated with the centrally located die units 52. Consequently, as the cam 61 moves axially through the die units a first plurality of beads 19a, 19b, 19c having progressively increased diameters are formed in sequential order, followed by sequential formation of a second plurality of equidiameter beads 19, and then by sequential formation of a third plurality of beads 19f, 192, 19d (not shown in FIG. 9 but visible in FIG. of progressively decreased diameters.

Reference to the aforesaid M. I. M. Coppens patents, and particularly to Patent No. 3,268,109, will reveal that there is there disclosed a method for forming shaped metal containers including a plurality of equidiameter peripheral beads wherein the material of the blank on each side of each bead being formed is permitted to move towards the bead, thus causing the blank to contract axially and wherein the relationship of radial expansion to axial contraction is controlled to produce a beaded sidewall in which the average net axial strain is on the order of 2% and less than 5%. Consistent with that desirable method, the apparatus disclosed in the aforesaid Luedi, Ullman et a1. and Bijvoet patents were developed to permit a controlled radial head expansion and axial blank contraction, although all beads produced in a given blank on a given apparatus are of the same diameter. While not critical to the present invention, the same desirable objective can also be achieved in conjunction with the formation of products in accordance with the invention.

Thus, referring to FIGS. 6 and 7, it will be observed that as the die units 30a-30e and SM expand radially, they also collapse axially (to the left as viewed in the drawings). As a consequence, the material of the blank on each side of each bead is permitted to move towards the head during the forming operation, thereby significantly shortening the axial length of the blank and controlling the axial strain created. Similarly, in the apparatus 40 shown in FIG. 8, the segments for the various die units 4111-41 and 4111 are supported by carriers 62 which are each coupled to one another by means of threaded sleeves 64 splined to and axially slidable on a rotatable shaft 65, the latter being rotatably driven from an input shaft 66 (coupled to a suitable power source, not shown) through gears 68, 69. Thus, as the die units are expanded outwardly, rotation of the shafts 66 and 65 cause the die units to collapse axially, again permitting the material on each side of each bead being formed to move towards the head. And, referring to FIG. 9, it will be observed that since the ends of blank 12 are not restrained and since the beads are formed one at a time, the material on each side of any given head is also free to move towards the bead dur ing its formation. Those interested in acquiring a more detailed description of the foregoing constructions are referred to the aforesaid Luedi, Ullman et al. and Bijovet patents.

It will, of course, be appreciated by those skilled in the art that the particular number of beads and furrows included in the tapered regions of the sidewall may vary, as may the angle of taper and/or the dimensions of the drum, all dependent upon numerous variable parameters such as container capacity, overall heighth and/ or depth of the container, the gauge of the materials used, etc. However, it has been found that when dealing with 55- gallon containers made of 24-gauge sheet steel from a blank 12 having an initial inside diameter of 22.5 inches, and wherein on the order of 26 beads are provided, excellent results are achieved when the following dimensions are maintained: the inside diameter D of blank 12 is on the order of 22.5 inches; the inside diameter D of bead 19a is on the order of 22.9 inches; the inside diameter of head 19b is on the order of 23.05 inches; the inside diameter of head is on the order of 23.2 inches; the inside diameter of all beads 19 is on the order of 23.32 inches; and the angle e of taper is on the order of three to four degrees (3 4).

I claim as my invention:

1. In a metal shipping container comprising a generally cylindrical sidewall having a diameter D and a pair of end members rigidly seamed to respective ones of the opposite extremities of said sidewall, said sidewall having a plurality of radially outwardly extending peripheral beads spaced axially from one another with the spacing between beads defining a plurality of radially inwardly extending peripheral furrows, and wherein the top portion of each of said beads and the bottom portions of the adjacent furrows define a smoothly curved radial crosssection; the improvement characterized in that the beads in the central portion of said container sidewall all have a diameter D where D is greater than D and the furrows in the central portion all have a common diameter less than D", while at least one extremity of said container sidewall includes n beads and n furrows where n is any selected whole integer with said It beads having a diameter D where D is greater than D and less than D and with said it furrows having a smaller diameter than the diameter of the furrows in said central portion and wherein when n is greater than one, the diameters of the n beads and n furrows progressively decrease from said central portion of said container sidewall towards the extremity thereof.

2. A metal shipping container as set forth in claim 1 further characterized in that the number of beads in said central portion is on the order of twenty and n is in the range of one to four.

3. A metal shipping container as set forth in claim 1 further characterized in that n equals three.

4. A metal shipping container as set forth in claim 3 further characterized in that D is on the order of 23.32 inches, and the diameters of the three beads at said container sidewall extremity are on the order of 23.2, 23.05, and 22.9 inches respectively from said central portion to said extremity.

5. A tubular metal sidewall for a shipping container, said sidewall being defined by a first plurality of axially spaced, equidiameter, radially outwardly extending peripheral beads with the spacing between adjacent beads defining a plurality of axially spaced, equidiameter, radially inwardly extending peripheral furrows, and a second plurality of axially spaced, radially outwardly extending peripheral beads alternating with axially spaced, radially inwardly extending peripheral furrows, characterized in that the diameter of the beads and furrows in said second plurality progressively decrease from said first plurality towards the adjacent extremity of said sidewall.

6. A tubular metal sidewall for a shipping container as set forth in claim 5 further characterized in that axially extending tangent lines to the beads defining said first plurality lie in a cylindrical surface and axially extending tangent lines to the beads defining said second plurality lie in a common frusto-conical surface with the intersection of said surfaces defining an angle therebetween.

7. A tubular metal sidewall for a shipping container as set forth in claim 6 further characterized in that said angle between said surfaces is in the order of three to four degrees (3-4).

8. A metal shipping container comprising, in combination, at least one end member and a sidewall, said end member and said sidewall being rigidly seamed together adjacent one end of the latter and defining a chime, said sidewall having a first plurality of axially spaced, equidiameter, radially outwardly extending peripheral beads with the spacing between adjacent beads defining a plurality of axially spaced, equidiameter, radially inwardly extending peripheral furrows, and a second plurality of axially spaced, radially outwardly extending peripheral beads alternating with axially spaced, radially inwardly extending peripheral furrows, characterized in that the diameters of the beads and furrows in said second plurality progressively decrease from said first plurality of beads toward said chime.

9. A metal shipping container as set forth in claim 8 further characterized in that axially extending tangent lines to the beads defining said first plurality lie in a cylindrical surface and axially extending tangent lines to the beads defining said second plurality lie in a common frusto-conical surface.

10. A metal shipping container as set forth in claim 9 further characterized in that all planes perpendicular to the axis of said frusto-conical surface and passing through said chime define circles with the frusto-conical surface having diameters greater than the outside diameter of said chime.

References Cited UNITED STATES PATENTS 327,254 9/1885 Graves 220-72 1,174,833 3/1916 Dougherty 220-72 3,268,109 8/1966 Coppens 220'72 3,349,600 10/1967 Bijvoet 72393 FOREIGN PATENTS 613,588 12/ 1960 Italy.

JOSEPH R. LECLAIR, Primary Examiner JAMES R. GARRETT, Assistant Examiner US. Cl. X.R. 

